Gammons was a featured writer at The Boston Globe for many years as the main journalist covering the Boston Red Sox. (1969–1975, 1978–1986), or as a national baseball columnist. For many years he was a colleague of other legendary Globe sports writers Will McDonough, Bob Ryan, and Leigh Montville. Between his two stints as a baseball columnist with the Globe, he was lead baseball columnist for Sports Illustrated (1976–78, 1986–90), where he covered baseball, hockey, and college basketball. Gammons also wrote a column for The Sporting News in the 1980s.

Gammons has also authored numerous baseball books, including Beyond the Sixth Game.

In 1988, he joined ESPN, where he served primarily as an in-studio analyst.[1] During the baseball season, he appeared nightly on Baseball Tonight and had regular spots on SportsCenter, ESPNEWS and ESPN Radio. He wrote an Insider column for ESPN.com and also wrote for ESPN The Magazine. The Globe reprinted some of his ESPN columns well into the 1990s. In 2006, Gammons was named as one of two field-level reporters for ESPN's Sunday Night Baseball, joining Bonnie Bernstein. He held that position through the 2008 season, when he moved exclusively to baseball.

After 20 years with ESPN, on December 8, 2009, Gammons announced that he would leave ESPN to pursue "new challenges" and a "less demanding schedule".[3] Gammons joined the MLB Network and MLB.com as on-air and online analyst. He also works for NESN.[4]

January 9, 2009 was proclaimed Peter Gammons day in the City of Boston. The proclamation was made by Michael Ross, president of the Boston City Council at the Hot Stove Cool Music Sports Roundtable at Fenway Park. 2010 marked the 10th anniversary of Hot Stove Cool Music, a charitable concert benefiting the Foundation To Be Named Later. At this event, Theo Epstein, Vice President and General Manager of the Boston Red Sox, announced a new scholarship in Gammons' name. The "Peter Gammons - Foundation To Be Named Later Scholarship presented by RISO" enables select Boston Public Schools students to attend college who otherwise might not have the chance.[7]

Peter returned to ESPN on Wednesday, September 20, 2006. He reported from Fenway Park on the 6 P.M. edition of SportsCenter and the 7 P.M. edition of Baseball Tonight. Gammons resumed his regular reporting coverage during the 2007 baseball season.[11]

Gammons has a penchant for indie rock and the blues, and is active in the Boston indie rock scene when his other commitments allow him the time; he has been sighted at several Midnight Oil shows, and has mentioned the band in several columns. He is also a fan of Pearl Jam, as he has talked about experiences at concerts as well as previous albums (as heard on various ESPN Radio shows.) With the assistance of a band of Boston musicians and former Boston Red Sox General Manager Theo Epstein, Gammons plays a FenderStratocaster and sings at the annual Hot Stove, Cool Music concert event to benefit Theo and Paul Epstein's Foundation To Be Named Later, a charity that raises funds and awareness for non-profit agencies serving disadvantaged youth in the Greater Boston area.

The Boston Baseball Band wrote a song about Gammons called "Jammin' With Peter Gammons." Gammons founded the Hot Stove Cool Music benefit concert series with sportswriter Jeff Horrigan, Casey Riddles, Debbi Wrobleski, Mindy d'Arbeloff and singer Kay Hanley in December 2000. The fundraiser now takes place twice each year, with one show in January and another in July or August.

Gammons is tightly connected to the Boston rock scene. He even served as minister at the November 2007 marriage of bassist Ed Valauskas (Gravel Pit, the Gentlemen) and singer Jennifer D'Angora (Downbeat 5, the Dents, Jenny Dee and the Deelinquents).

^Gleeman, Aaron (November 1, 2010). "Yadier Molina leads fifth annual "Fielding Bible Awards"". NBCSports.com. Retrieved November 18, 2010. Voted on by a 10-person panel that includes Bill James, Peter Gammons, Joe Posnanski, Rob Neyer, and John Dewan as well as the entire video scouting team at Baseball Info Solutions, the award sets out to recognize the best defensive player at each position, regardless of league.